The present invention relates to a multi-piece solid golf ball composed of a core, an envelope layer, an intermediate layer and a cover that have been formed as successive layers. More specifically, the invention relates to a multi-piece solid golf ball for professionals and other skilled golfers which is endowed with an excellent flight performance and good controllability.
A variety of golf balls have hitherto been developed for professionals and other skilled golfers. Of these, multi-piece solid golf balls in which the hardness relationship between an intermediate layer encasing the core and the cover layer has been optimized are in wide use because they achieve both a superior distance in the high head speed range and good controllability on shots taken with an iron and on approach shots. Another important concern is the proper selection of thicknesses and hardnesses for the respective layers of the golf ball in order to optimize not only flight performance, but also the feel of the ball when played and the spin rate of the ball after being struck with the club, particularly given the large influence of the spin rate on control of the ball. A further key concern in ball development, arising from the desire that golf balls also have durability under repeated impact and scuff resistance against burr formation on the surface of the ball when repeatedly played with different types of clubs, is how best to protect the ball from external factors.
The three-piece solid golf balls having an outer cover layer formed primarily of a thermoplastic polyurethane which are disclosed in U.S. Pat. No. 6,592,470, U.S. Pat. No. 6,679,791, U.S. Pat. No. 6,533,683, U.S. Pat. No. 6,814,676, U.S. Pat. No. 6,663,507 and U.S. Pat. No. 6,702,694 were intended to meet such a need. However, because this golf ball does not have a sufficiently reduced spin rate when hit with a driver, it is often unable to deliver a distance that is acceptable to professionals and other skilled golfers.
Meanwhile, efforts to improve the flight and other performance characteristics of golf balls have led to the development of balls having a four-layer construction, i.e., a core encased by three intermediate or cover layers, that allows the ball construction to be varied among the several layers at the interior. Such golf balls have been disclosed in, for example, JP-A 9-248351, JP-A 10-127818, JP-A 10-127819, JP-A 10-295852, JP-A 10-328325, JP-A 10-328326, JP-A 10-328327, JP-A 10-328328, JP-A 11-4916 and JP-A 2004-180822.
Yet, as golf balls for the skilled golfer, the above balls provide a poor balance of distance and controllability or fall short in terms of achieving a lower spin rate on shots with a driver, thus limiting the degree to which the total distance can be increased. Moreover, with these golf balls, it has been difficult to achieve in the same ball a good spin rate-lowering effect, good rebound and good durability.